Glutathione is a known constituent of mammalian cells. Increased levels thereof are known to diminish the cytotoxic effects of radiation, cadmium, acetominophen, and anticancer drugs such as BCNU (i.e., 1,3-bis(2-chloroethyl)-1-nitosourea) and cyclophosphamide. Since glutathione itself does not effectively cross cell membranes, alternative strategies of increasing intracellular levels of glutathione have been developed. The most effective and generally useful of these is administering glutathione monoesters. Conventionally these monoesters are prepared by reacting glutathione with an alcohol in the presence of an acid and have been, in all cases, initially isolated as acid salts. Administration parenterally to mammals of acid salts requires coadministration of neutralizing agent. Such neutralizing agent increases the osmolarity and ionic strength of the adminstered solution, and in typical pharmacological quantities such increases may significantly disturb system balances. Therefore, the isolated acid salts are typically converted to the neutral esters prior to administration. Despite the inconvenience of and decreased yield attendant to isolating first the salt and then the neutral ester, a procedure for preparing neutral esters without first isolating the acid salts has not heretofore been disclosed.